Garnet pyroxenites are the most common deep-lithospheric xenolith assemblages found in Miocene volcanic rocks erupted through the central part of the Cretaceous Sierra Nevada Batholith (SNB).  We present elemental concentrations and isotopic ratios to argue that the SNB granitoids and the pyroxenite xenoliths are, respectively, the melts and residues/cumulates resulting that resulted from partial melting/fractional crystallization at depths exceeding 35-40 km.  The estimated major element chemistry of the protolith resembles a high-Mg, low-Al hydrous basalt or basaltic andesite.  We propose that certain segments of the Cordilleran batholiths may have originated by petrologic processes analogous to those which let to the extraction of the voluminous granitoids that make up the cratonic nuclei of the continents.

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